Make repairIntervalsInRange() more robust. There are now no longer any liveness-
related failures when running 'make check' without LiveVariables with the
verifier enabled. Some of the remaining failures elsewhere may still be fallout
from incorrect updating of LiveIntervals or the few missing cases left in the
two-address pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175672 91177308-0d34-0410-b5e6-96231b3b80d8
Find anchoring end points for repairIntervalsInRange and repairIndexesInRange
automatically.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175673 91177308-0d34-0410-b5e6-96231b3b80d8
Only use LiveIntervals in TwoAddressInstructionPass, not a mix of Liveintervals
and SlotIndexes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175674 91177308-0d34-0410-b5e6-96231b3b80d8